Hello Chuck,
This is a really hard one to comment on. I feel your pain. I don't have an answer but just a few things to use for decisions.
1. The guys who have commented already have good ideas.
2. The basic concept of Stovebolt, and it's members, is DIY. Many have never gone to a shop. I have not. A few here have, with mixed experiences.
3. HOA's can be a real pain.
4. Don't use whether you will sell it for a profit or loss as a deciding factor. That factor is unknowable. The only possible profit is from a DIY build.
5. If you can't afford it, don't do it. If the feeling is there after a few days or a week, do it.
6. There is more than a 50/50 chance the estimate will go UP. That's what ALL estimates do. I know the guy is honest but you will become hostage to price and time.
7. The truck will be in the shop WAY longer than estimated.
8. The hot rod version of your truck will have a greater chance of becoming upsidedown than the restored or semi restored or driver version.
9. Renting a place is good only if you have all the equipment and tools there for some of the major mods you listed......and know how to do them, be there for shipments.
10. This type of mod rod can take some of us 3-5 years and more.
11. You told him "only want the basics done". You don't have any basics.
12. The price he gave is "reasonable".......but it's one of the reasons I don't use a shop.
13. I have PM'ed you a suggestion not suitable for Stovebolt community.
You list 4 project vehicles in your signature. Where are these stored? Can that place be used for DIY?
I thought Texas was the wide open spaces but I see San Antonio is pretty dense. Gotta go a ways out of town to get into the ranches and farms with possible buildings to use. I think right now I would reach out to local clubs in the area and meet and greet. Somebody will have a place or advice more atuned to that area. Maybe even a retired guy who would work on it and you could work with him at his place. Anyway just some food for thought. Sleep on it a few nights.
The paint and upholstery could push it to $45K ................Just trying to calm you down

When you call his price outrageous, I tend to agree. Even though it's a price which includes parts, shipping of parts, lots of labor, overhead and profit. But your comment and the fact you are having a shop install used stuff tells me you are on a budget and are not going to enjoy the shop gig. Like I would be, you are already stressed and at your limit of $$. So when the surprises he discovers, problems, increase in cost, excuses and time extension come, it will be too late. If I read all that into "outrageous", then that road is not for you at this time. Keep control of your truck. Farm it out a little, find that old retired guy, find a good place to work on it or buy one partially finished per my PM....and possibly reduce the modifications.
Martin is exactly right, your parts are over $13000. Right now there is an EXTREME shortage of all kinds of parts. Wait times are EXTREME. Inflation is looming. Many of those parts will be out of stock and have several months back order wait times. Shipping prices are increasing especially the heavy item freight rates.
So now I do have an answer. Buy a truck already done to the point you want. That is the definite answer. Cheaper, faster, known quality and workmanship, seeing what you are getting rust wise............ at a known and negotiable price. No tax. Bam!
Finding, traveling, inspecting and negotiating is the new task. Sell your 51 to recoup. Sounds like it's pretty rusted if you need a new floor. That alone is a supper labor cost.
I have actually thought it all thru for you in real time. I never cease to be amazed at myself. Awesome.